proBNP
N-terminal pro-B-type natriuretic peptide — a cardiac biomarker released when heart muscle is stretched or stressed. Elevated proBNP in dogs indicates cardiac chamber enlargement and helps detect heart disease before clinical signs appear.
proBNP (N-terminal pro-B-type natriuretic peptide) is a protein fragment released into the bloodstream by cardiac muscle cells when the heart chambers are stretched beyond normal. It serves as a quantitative biomarker of cardiac stress — the higher the concentration, the greater the cardiac chamber enlargement or pressure overload.
How It Works
When the heart muscle (myocardium) is stretched — due to volume overload in dilated cardiomyopathy or pressure overload in mitral valve disease — cardiomyocytes release a precursor protein (proBNP) that is cleaved into two fragments: the biologically active BNP (which promotes natriuresis and vasodilation) and the inactive NT-proBNP (the fragment measured by the test).
NT-proBNP has a longer half-life than BNP, making it a more stable and reliable laboratory measurement.
Clinical Applications in Dogs
Screening for Occult Heart Disease
proBNP testing is most valuable for detecting heart disease before clinical signs appear:
- Doberman Pinschers: annual proBNP screening alongside Holter monitoring and echocardiography for occult dilated cardiomyopathy
- Cavalier King Charles Spaniels: monitoring for progression of mitral valve disease
- Large/giant breeds: screening for subclinical cardiac disease as part of senior wellness panels
Differentiating Cardiac vs. Respiratory Disease
When a dog presents with cough or respiratory distress, proBNP helps differentiate cardiac causes (elevated proBNP) from primary respiratory disease (normal proBNP). This distinction is clinically important because treatments differ substantially.
Monitoring Treatment Response
Serial proBNP measurements can track response to cardiac medications. Declining levels suggest effective treatment; rising levels may indicate disease progression.
Reference Values
| Category | NT-proBNP (pmol/L) | Interpretation |
|---|---|---|
| Normal | <900 | Heart disease unlikely |
| Equivocal | 900-1800 | Further testing recommended |
| Elevated | >1800 | Cardiac disease probable |
Values vary by laboratory and assay. Results should always be interpreted alongside physical examination, radiographs, and ideally echocardiography.
Limitations
proBNP can be elevated by renal disease (reduced clearance), pulmonary hypertension, and severe systemic illness. It should not be used as a standalone diagnostic test but rather as part of a cardiac screening protocol.